Novel compounds that exhibit specific molecular recognition of mixed nucleic acid sequences and bind in the DNA minor groove as a dimer

ABSTRACT

Asymmetric derivatives of furamidines with one of the phenyl rings of furamidine replaced with a benzimidazole have been found by quantitative footprinting analyses to bind GC containing sites on DNA more strongly than to pure AT sequences. These compounds have been shown to bind in the minor groove at specific GC containing sequences of DNA in a highly cooperative manner as a stacked dimer. Compounds of the present invention find use in selectively binding mixed sequence DNA, and may also be used in methods of regulating gene expression, methods of treating opportunistic infections and cancer, as well as in methods of detecting certain sequences of DNA.

RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/172,863, filed Dec. 20, 1999, which is incorporatedherein by reference in its entirety.

STATEMENT OF FEDERAL SUPPORT

[0002] This invention was made with United States Government supportunder grant number AI-33363 from the National Institutes of Health. TheUnited States Government has certain rights to this invention.

FIELD OF THE INVENTION

[0003] This invention relates to novel compounds that recognize mixedsequences (i.e., GC as well as AT base pairs), and specifically bind theDNA minor groove through dimer formation.

BACKGROUND OF THE INVENTION

[0004] Design and discovery of molecules that can regulate geneexpression in cells in a desirable and predictable manner is a centralgoal of research at the interface of chemistry and biology. See, e.g.,Schreiber, S. L., Bioorg. Med. Chem. 6, 1127-1152 (1998); C. Denison andT. Kodadek, Chem. Biol. 5, R129-R145 (1998); A. G. Papavassiliou,Molecular Medicine Today 358-366 (1998); R. E. Bremer, et al., Chem.Biol. 5, 119-133 (1998); J. Gottesfeld et al., Nature 387, 202-205(1997); H. Iida, Current Opinion Biotechnology 10, 29-33 (1999). Thedeveloping field of “chemical genetics” requires molecules that have thenecessary selectivity to recognize target genes. See, e.g., S.Schreiber, supra, and Schreiber, S., FASEB J. 11,p.M1 (1997).

[0005] A number of aromatic diamidines have been shown to bind to theminor-groove of DNA, and to exhibit useful antimicrobial activity.Various hypotheses of the mode of antimicrobial action of the arylamidines have been proposed. However, evidence is growing that thesecompounds function by complex formation with DNA and subsequentselective inhibition of DNA dependent microbial enzymes. Intervention intranscription control has been demonstrated and seems to be a plausiblemode of action for structurally diverse minor groove binders. B. P. Das,et al., J. Med. Chem. 20, 531-536 (1977); D. W. Boykin, et al., J. Med.Chem. 36, 912-916 (1995); A. Kumar et al., Eur. J. Med. Chem. 31,767-773 (1996); R. J. Lombardy, et al., J. Med. Chem. 31, 912-916(1996); R R. Tidwell. et al., Antimicrob. Agents Chemother. 37,1713-1716 (1993); R. R. Tidwell, R. R. and C. A. Bell, “Pentamidine andRelated Compounds in Treatment of Pneumocystis carinii Infection,” inPneumocystis carinii, (Marcel Decker; New York, 561-583 (1993)); D.Henderson, and L. H. Hurley, Nature Med. 1, 525-527 (1995); J. Mote,Jr., et al., J. Mol. Biol. 226, 725-737 (1994); and D. W. Boykin, etal., J. Med. Chem. 41, 124-129 (1998).

[0006] Organic cations that bind in the DNA minor groove also havebiological activities that range from anti-opportunistic infection toanticancer properties. See e.g., C. Bailly, in Advances in DNASequence-Specific Agents, Vol. 3, pp. 97-156 (L. H. Hurley, Ed. JAIPress Inc., London, UK, 1998); J. A. Mountzouris and L. H. Hurley, inBioorganic Chemistry: Nucleic Acids, pp. 288-323, (S. M. Hecht, Ed.,Oxford Univ. Press, New York, 1996); E. Hildebrant, et al., J. Euk.Microbiol. 45, 112 (1998); and K. Hopkins et al., J. Med. Chem. 41, 3872(1998). Such compounds have provided a wealth of fundamental informationabout nucleic acid recognition properties, and they continue to beimportant models in the study of nucleic acid complexes.

[0007] The DNA minor-groove and AT sequence recognition properties ofmolecules of this series have been probed extensively for more than 30years. See, e.g., C. Zimmer and U. Wahnert, Prog. Biophys. Mol. Biol.47, 31 (1986); B. H. Geierstanger and D. E. Wemmer, Annu. Rev. Biophys.Biomol. Struct. 24, 463 (1995); W. D. Wilson, in Nucleic Acids inChemistry and Biology, Chapter 8 (G. M. Blackburn and M. J. Gait, Eds.,IRL Press, Oxford, U.K., 1996). The compound netropsin (see FIG. 1) wasthe first minor groove-binding compound crystallized with a B-form DNA,and the structure of the complex provided clear suggestions about themolecular basis for AT base pair sequence-specific recognition. M. L.Kopka, et al., Proc. Natl. Acad. Sci. 82, 1376 (1985). The structure ofnetropsin also led to the development of minor-groove binding netropsinanalogs, the lexitropsins, that could specifically recognize GC basepairs and could thus have extended sequence recognition capability. See,J. W. Lown et al., Biochemistry 25, 7408 (1986); M. L. Kopka and T. A.Larsen, in Nucleic Acid Targeted Drug Design, pp. 303-374C (L. Probstand T. J. Perun, Eds., Marcel Dekker Inc., New York, 1992); and M. L.Kopka et al., Structure 5, 1033 (1997). Initial efforts in the design ofsuch analogs did provide compounds with enhanced recognition of GC basepairs, but unfortunately, the specificity obtained was not significant.A breakthrough in this area occurred with the discovery that themonocationic compound distamycin (FIG. 1) could bind into the minorgroove of some AT sequences of DNA as a stacked, antiparallel dimer. SeeJ. G. Pelton and D. E. Wemmer, Proc. Natl. Acad. Sci. 86, 5723 (1989),and J. G. Pelton and D. E. Wemmer, J. Am. Chem. Soc. 112, 1393 (1990).

[0008] One of the early recognition principles for AT sequences was thefact that the minor groove is narrower in AT than in GC regions, and itis perhaps the most surprising feature of the dimer complex that theminor groove in B-form DNA can readily expand to the width required fordimer binding. The expansion of the groove not only allows the dimer tobind but also provides for recognition of both strands in the duplexthrough complementary strand recognition by the two molecules of thedimer. Replacement of pyrrole group in distamycin by imidazole providedimproved GC recognition specificity with dimer complexes and currentdesign efforts in this system have reached a high level of success. Seee.g., C. L. Kielkopf, et al., Nature Struct. Biol. 5, 104 (1998); S.Whiteet al., Nature 391, 468 (1998); C. L. Kielkopf et al., Science 282,111 (1998); S. E. Swalleyet al., J. Am. Chem. Soc 121, 1113 (1999); andD. M. Herman, et al., J. Am. Chem. Soc 121, 1121 (1999). With recentincorporation of hydroxypyrole groups as a recognition unit, AT and TAas well as GC and CG base pairs can now be effectively distinguished inDNA sequences by pyrrole-imidazole polyamides related to distamycin.

[0009] The pyrrole-imidazole polyamide system is the only one of thewell-known minor-groove binding motifs that has been found to form thestacked-dimer recognition unit. Even netropsin, the first minor-groovebinding agent to be structurally characterized in detail and adicationic relative of the monocation distamycin (FIG. 1), does not forma dimer recognition unit. A recent crystal structure of a 2:1netrospin-DNA complex found that the two netropsin molecules in thecomplex bound in the minor groove as tandem monomer units instead of theside-by-side dimer observed with distamycin. See e.g., X. Chen, et al.,J. Mol. Biol. 267, 1157 (1997); X. Chen, et al, Nucleic Acids Res. 26,5464 (1998); and X. Chen, et al, Nature Struct. Biol. 1, 169 (1994). Thetwo charges of netropsin as well as other minor groove agents, such asthe faran derivatives shown in FIG. 1, have been postulated to preventstacked-dimer formation.

[0010] Recent evidence suggests that some monocationic cyanine dyes canform an array of stacked dimers in the DNA minor groove. See J. L.Seifert, et al., J. Am. Chem. Soc. (in press, 1999). There are, however,other monocationic minor-groove agents, such as Hoechst 33258 (see FIG.1 and analogs, that apparently do not form dimer DNA recognition motifs.These results indicate that the electrostatic and stereochemicalrequirements for minor-groove recognition of DNA by dimers are veryrestrictive, and further suggest that stacked dimer formation bydications is unlikely.

SUMMARY OF THE INVENTION

[0011] The present invention is based on the inventors' surprisingdiscovery of a new class of organic dications, based on unfused-aromaticsystems, that selectively recognize mixed DNA sequences (i.e., AT aswell as GC base pairs) in a manner that is very sensitive to compoundstructure. These are the first non-peptide compounds that havemixed-sequence recognition capability and the result is particularlypromising, since similar compounds readily enter cells and havegenerally low toxicity. See K. Hopkins et al., J. Med. Chem. 41,3872-3878 (1998). A surprising feature of this discovery is thatrecognition occurs through highly cooperative dimer formation at the DNAbinding site, a process that has been predicted not to occur fordications. The series of compounds provides a synthetically accessiblenew motif for specific recognition of DNA and control of geneexpression. Such compounds accordingly find use in numerous therapiesand treatments, including the treatment and prevention of opportunisticinfections, cancer and other diseases of cell proliferation, anddisorders of genetic origin (i.e., diseases caused by mutations of DNAand the like). Additionally, certain of the compounds of the presentinvention are fluorescent, and thus are useful for the detection ofcertain specific sequences recognized by the compounds of the invention.

[0012] Accordingly, a first aspect of the present invention is acompound of Formula I:

[0013] wherein:

[0014] X is selected from the group consisting of O, S, and NH;

[0015] Y is CH or N;

[0016] A is CH or N;

[0017] B is selected from the group consisting of NH, O or S;

[0018] R₁ is selected from the group consisting of H, loweralkyl,halogen, oxyalkyl, oxyaryl, and oxyarylakyl;

[0019] R₂ and R₉ are each independently selected from the groupconsisting of H, H₂, hydroxy, lower alkyl, cycloalkyl, aryl, alkylaryl,alkoxyalkyl, hydroxycycloalkyl, alkoxycycloalkoxy, hydroxyalkyl,aminoalkyl and alkylaminoalkyl; and

[0020] R₃, R₄, R₁₃ and R₁₄ are each independently selected from thegroup consisting of H, lower alkyl, alkoxyalkyl, cycloalkyl, aryl,alkylaryl, hydroxyalkyl, aminoalkyl, and alkylaminoalkyl,or R₃ and R₄together or R₁₃ and R₁₄ together represent a C₂ to C₁₀ alkyl,hydroxyalkyl, or alkylene, or R₃ and R₄ together or R₁₃ and R₁₄ togetherare:

[0021] wherein n is a number from 1 to 3, and R₁₀ is H or—CONHR₁₁NR₁₅R₁₆, wherein R₁₁ is lower alkyl and R₁₅ and R₁₆ are eachindependently selected from the group consisting of H and lower alkyl;

[0022] L is selected from the group consisting of:

[0023] wherein R₅, R₆, R₇, and R₈ are each individually selected fromthe group consisting of H, alkyl, halo, aryl, arylalkyl, aminoalkyl,aminoaryl, oxoalkyl, oxoaryl, and oxoarylalkyl; and wherein saidcompound of Formula I binds mixed-sequence DNA in the minor groove in adimer formation. In a preferred embodiment of the invention, thecompound of Formula I is a dication, L is:

[0024] A is N; B is NH; X is O; Y is CH; R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉and R₁₄ are each H; and R₃ and R₁₃ are each H₂.

[0025] A second aspect of the present invention is a method ofselectively binding mixed sequence DNA comprising contacting a sample ofDNA with a compound of Formula I.

[0026] A third aspect of the present invention is a method of detectingmixed DNA sequences comprising contacting a sample of DNA with afluorescent compound of Formula I, and then observing fluorescence inthe sample, the observation of fluorescence indicating that mixed DNAsequences have been bound.

[0027] A fourth aspect of the invention is a pharmaceutical formulationcomprising a compound of Formula I in a pharmaceutically acceptablecarrier.

[0028] Additional aspects of the invention include methods ofcontrolling gene expression, methods of treating microbial infection,methods of treating cancer and other disorders of cell proliferation,and methods of treating disorders of genetic origin (i.e., where thedisease state is caused by a gene mutation or mutations).

[0029] Other aspects of the present invention include the use of anactive compound as described above for the preparation of a medicamentfor controlling gene expression, or medicament for treating a microbialinfection, or a method of treating a disorder of genetic origin in asubject in need thereof.

[0030] The foregoing and other aspects of the present invention areexplained in detail in the specification set forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031]FIG. 1. sets forth the chemical structures for the minor-groovebinding compounds netropsin, distamycin, Hoechst 33258, furamidine(DB75), DB270, and DB293. FIG. 1 also sets forth the DNA sequences foroligo1, oligo2, oligo2-1 and oligo2-2, as described herein.

[0032]FIG. 2. illustrates the results of a quantitative DNase Ifootprinting titration experiment with the compound DB293 on the 265 bpDNA fragment as described herein. The EcoRI-PvuII restriction fragmentfrom plasmid pBS was 3′-end labeled at the EcoRI site with [α-³²P]dATPin the presence of AMV reverse transcriptase. As illustrated in FIG. 2A,the products of the DNase I digestion were resolved on an 8%polyacrylamide gel containing 8M urea. Drug concentrations are (lanes1-11) 0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3.0 μM for DB 293and (lanes 12-15) 0, 1, 2 and 5 μM for DB270. Tracks labeled ‘G’represent dimethylsulphate-piperidine markers specific for guanines. Thetrack labeled DNA contained no drug and no enzyme. Numbers at the rightside of the gel refer to the numbering scheme of the fragment. Therectangles on the left side refer to the positions of (open box) anAT-rich and (filled box) a GC-rich binding site for DB293. FIG. 2B is agraphical illustration of footprinting plots for the binding of DB293 to(open circles) the AT site 5′-AATTAA and (filled squares) the GC-richsite 5′-ACCATG. The relative band intensity R corresponds to the ratioI_(c)/I_(o) where I_(c) is the intensity of the band at the ligandconcentration c and I_(o) is the intensity of the same band in theabsence of DB293. The differential cleavage plots shown in FIG. 2Ccompare the susceptibility of the DNA to cutting by DNase I in thepresence of (filled circles) 5 μM DB270 or (open squares) 1.5 μM DB293.Deviation of points towards the lettered sequence (negative values)corresponds to a ligand-protected site and deviation away (positivevalues) represents enhanced cleavage. The vertical scale is in units ofln(f_(a))−ln(f_(c)), where f_(a) is the fractional cleavage at any bondin the presence of the drug and f_(c) is the fractional cleavage of thesame bond in the control. The results are displayed on a logarithmicscale for the sake of convenience. The rectangles below the sequenceshow the positions of (open box) the AT binding site and (filled box)the GC-rich site.

[0033]FIG. 3 sets forth Scatchard plots of the results for binding ofDB293 and DB270 to oligo1 and oligo2-1 along with best fit bindingcurves are shown: closed triangles and open triangles are for DB293 andDB270, respectively, binding to oligo1. Closed circles and open circlesare for DB293 and DB270 binding to oligo2-1, respectively Because of theweak binding of DB270 to oligo2-1, the results were fit with theassumption of a single DB270 binding to the duplex. Sensorgrams with thedata for this plot are shown in FIG. 6.

[0034]FIG. 4. is a two-dimensional COSY spectra of the TH6-TCH3 spectralregion shown for (top, A) free DNA; (middle, B) a 1:1 ratio sample ofDB293 to oligo2-1; and (bottom, C) a 2:1 ratio. Signals for the free DNAand for the 2:1 complex in the 1:1 ratio sample are indicated byconnecting lines to the top and bottom spectra.

[0035]FIG. 5 illustrates Tm curves as a function of ratio for complexesof DB270 and DB293 with oligo 2-1. Closed circles indicate free DNA;closed triangles and open triangles indicate DB293 at 1:1 and 2:1ratios, respectively, and closed squares and open squares indicate DB270at 1:1 and 2:1 ratios, respectively.

[0036]FIG. 6 sets forth sensorgrams for binding of DB270 and DB 293 to(top, A) oligo2-1 and (bottom, B) oligo1. Drug concentrations range from1 nM to 1 μM.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] The present invention will now be described more fullyhereinafter with reference to the accompanying drawings, in whichpreferred embodiments of the invention are shown. This invention may,however, be embodied in different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart.

[0038] Unless otherwise defined, all technical and scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which this invention belongs. All publications,patent applications, patents, and other references mentioned herein areincorporated by reference in their entirety.

[0039] Nucleotide sequences are presented herein by single strand only,in the 5′ to 3′ direction, from left to right. Nucleotides arerepresented herein in the manner recommended by the IUPAC-IUBBiochemical Nomenclature Commission in accordance with 37 CFR §1.822 andestablished usage. See, e.g., PatentIn User Manual, 99-102 (November1990) (U.S. Patent and Trademark Office).

[0040] Certain objects, advantages and novel features of the inventionwill be set forth in the description that follows, and will becomeapparent to those skilled in the art upon examination of the following,or may be learned with the practice of the invention.

[0041] As used herein the term “alkyl” refers to C₁₋₁₀ inclusive,linear, branched, or cyclic, saturated or unsaturated (i.e., alkenyl andalkynyl) hydrocarbon chains, including for example, methyl, ethyl,propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, octyl,ethenyl, propenyl, butenyl, pentenyl, hexenyl, octenyl, butadienyl,propynyl, butynyl, pentynyl, hexynyl, heptynyl, and allenyl groups. Asused herein, the term “acyl” refers to an organic acid group wherein the—OH of the carboxyl group has been replaced with another substituent(i.e., as represented by RCO—, wherein R is an alkyl or an aryl group).As such, the term “acyl” specifically includes arylacyl groups. Specificexamples of acyl groups include acetyl and benzoyl. As used herein, theterm “aryl” refers to 5 and 6-membered hydrocarbon and heterocyclicaromatic rings. Specific examples of aryl groups include but are notlimited to cyclopentadienyl, phenyl, furan, thiophene, pyrrole, pyran,pyridine, imidazole, isothiazole, isoxazole, pyrazole, pyrazine,pyrimidine, and the like. The term “alkoxyl” as used herein refers toC₁₋₁₀ inclusive, linear, branched, or cyclic, saturated or unsaturatedoxo-hydrocarbon chains, including for example methoxy, ethoxy, propoxy,isopropoxy, butoxy, t-butoxy, and pentoxy. The term “aryloxyl” as usedherein refers to phenyloxyl or hexyloxyl, and alkyl, halo, or alkoxylsubstituted phenyloxyl or hexyloxyl. As used herein, the terms“substituted alkyl” and “substituted aryl” include alkyl and arylgroups, as defined herein, in which one or more atoms or functionalgroups of the aryl or alkyl group are replaced with another atom orfunctional group, including for example, halogen, aryl, alkyl, alkoxy,hydroxy, nitro, amino, alkylamino, dialkylamino, sulfate, and mercapto.The terms “halo,” “halide,” or “halogen” as used herein refer to fluoro,chloro, bromo, and iodo groups.

[0042] As used herein, the term “mixed sequence DNA” refers to asequence of DNA that comprises GC base pairs and AT base pairs.

[0043] Compounds of Formula I of the present invention (hereinafterreferred to as the “active compounds”) are useful in binding mixedsequences of DNA, i. e., GC as well as AT base pairs. Unexpectedly, theactive compounds bind in the minor groove of DNA at specific GCcontaining sequences in a highly cooperative manner as stacked dimers.Because of the ability of the compounds of the present invention to bindto specific and mixed sequences of DNA, they are useful in controllinggene expression by, for example, intervening in gene transcription.Accordingly, the active compounds may find pharmaceutical use in thetreatment of opportunistic infections such Pneumocystis carinii, in thetreatment of cancers and other disorders of proliferation, and in thetreatment of genetic disorders caused by, for example, mutations inparticular genes (e.g., cystic fibrosis, adult polycystic disease,Huntington's disease, myotonic dystrophy, neurofibromatosis, etc.).Moreover, since certain compounds of the present invention arefluorescent (ie., DB293, shown in FIG. 1), they are useful in detectingthe particular DNA sequences bound by the compounds through fluorescencedetection methods known in the art.

[0044] The active compounds of the present invention may be prepared bythe methods set forth in K. Hopkins et al., J. Med. Chem. 41,3872-3878(1998). The active compounds of the present invention may alsobe prepared by the methods set forth in R. Kada et al., Collect. Czech.Chem. Comm. 38, 1700-1704 (1973), modified as described below, thedisclosure of which is also incorporated herein in its entirety.Additionally, the active compounds may be administered aspharmaceutically acceptable salts. Such salts include the gluconate,lactate, acetate, tartarate, citrate, phosphate, borate, nitrate,sulfate, and hydrochloride salts. The salts of the present invention maybe prepared, in general, by reacting two equivalents of the basecompound with the desired acid, in solution. After the reaction iscomplete, the salts are crystallized from solution by the addition of anappropriate amount of solvent in which the salt is insoluble.

[0045] As noted above, the methods of the present invention are usefulfor treating opportunistic microbial infections such as, for example, P.carinii and Giardia lamblia. The compounds may also be useful intreating fungal infections such as Candida albicans, Cryptococcusneoformans, Aspergillus fumigatus, Fusarium solani, and combinationsthereof. The methods of the invention are useful for treating theseconditions in that they inhibit the onset, growth, or spread of thecondition, cause regression of the condition, cure the condition, orotherwise improve the general well-being of a subject afflicted with, orat risk of contracting the condition.

[0046] The compounds of the present invention are useful not only inmethods for treating infections and other disorders, but also in methodsof inhibiting enzymes such as topoisomerase.

[0047] Subjects to be treated by the methods of the present inventionare typically human subjects, although the methods of the presentinvention may be useful with any suitable subject known to those skilledin the art.

[0048] As noted above, the present invention provides pharmaceuticalformulations comprising the aforementioned active compounds, orpharmaceutically acceptable salts thereof, in pharmaceuticallyacceptable carriers for oral, intravenous, or aerosol administration asdiscussed in greater detail below. Also, the present invention providessuch compounds or salts thereof which have been lyophilized and whichmay be reconstituted to form pharmaceutically acceptable formulationsfor administration, as by intravenous or intramuscular injection.

[0049] The therapeutically effective dosage of any specific compound,the use of which is in the scope of present invention, will varysomewhat from compound to compound, and patient to patient, and willdepend upon the condition of the patient and the route of delivery. As ageneral proposition, a dosage from about 0.1 to about 50 mg/kg will havetherapeutic efficacy, with all weights being calculated based upon theweight of the active compound, including the cases where a salt isemployed. Toxicity concerns at the higher level may restrict intravenousdosages to a lower level such as up to about 10 mg/kg, with all weightsbeing calculated based upon the weight of the active base, including thecases where a salt is employed. A dosage from about 10 mg/kg to about 50mg/kg may be employed for oral administration. Typically, a dosage fromabout 0.5 mg/kg to 5 mg/kg may be employed for intramuscular injection.Preferred dosages are 1 μmol/kg to 50 μmol/kg, and more preferably 22μmol/kg and 33 μmol/kg of the compound for intravenous or oraladministration. The duration of the treatment is usually once per dayfor a period of two to three weeks or until the condition is essentiallycontrolled. Lower doses given less frequently can be usedprophylactically to prevent or reduce the incidence of recurrence of theinfection.

[0050] In accordance with the present method, pharmaceutically activecompounds as described herein, or pharmaceutically acceptable saltsthereof, may be administered orally as a solid or as a liquid, or may beadministered intramuscularly or intravenously as a solution, suspension,or emulsion. Alternatively, the compounds or salts may also beadministered by inhalation, intravenously or intramuscularly as aliposomal suspension. When administered through inhalation the activecompound or salt should be in the form of a plurality of solid particlesor droplets having a particle size from about 0.5 to about 5 microns,and preferably from about 1 to about 2 microns.

[0051] The present invention also provides a pharmaceutical compositionsuitable for intravenous or intramuscular injection. The pharmaceuticalcomposition comprises a compound of Formula (I) described herein, or apharmaceutically acceptable salt thereof, in any pharmaceuticallyacceptable carrier. If a solution is desired, water is the carrier ofchoice with respect to water-soluble compounds or salts. With respect tothe water-insoluble compounds or salts, an organic vehicle, such asglycerol, propylene glycol, polyethylene glycol, or mixtures thereof,may be suitable. In the latter instance, the organic vehicle may containa substantial amount of water. The solution in either instance may thenbe sterilized in a suitable manner known to those in the art, andtypically by filtration through a 0.22 micron filter. Subsequent tosterilization, the solution may be dispensed into appropriatereceptacles, such as depyrogenated glass vials. Of course, thedispensing is preferably be done by an aseptic method. Sterilizedclosures may then be placed on the vials and, if desired, the vialcontents may be lyophilized.

[0052] In addition to compounds of Formula (I) or their salts, thepharmaceutical compositions may contain other additives, such aspH-adjusting additives. In particular, useful pH-adjusting agentsinclude acids, such as hydrochloric acid, bases or buffers, such assodium lactate, sodium acetate, sodium phosphate, sodium citrate, sodiumborate, or sodium gluconate. Further, the compositions may containmicrobial preservatives. Useful microbial preservatives includemethylparaben, propylparaben, and benzyl alcohol. The microbialpreservative is typically employed when the formulation is placed in avial designed for multidose use. Of course, as indicated, thepharmaceutical compositions of the present invention may be lyophilizedusing techniques well known in the art.

[0053] In yet another aspect of the present invention, there is providedan injectable, stable, sterile composition comprising a compound ofFormula (I), or a salt thereof, in a unit dosage form in a sealedcontainer. The compound or salt is provided in the form of alyophilizate which is capable of being reconstituted with a suitablepharmaceutically acceptable carrier to form a liquid compositionsuitable for injection thereof into a subject. The unit dosage formtypically comprises from about 10 mg to about 10 grams of the compoundor salt. When the compound or salt is substantially water-insoluble, asufficient amount of emulsifying agent which is physiologicallyacceptable may be employed in sufficient quantity to emulsify thecompound or salt in an aqueous carrier. One such useful emulsifyingagent is phosphatidyl choline.

[0054] Other pharmaceutical compositions may be prepared from thewater-insoluble compounds disclosed herein, or salts thereof, such asaqueous base emulsions. In such an instance, the composition willcontain a sufficient amount of pharmaceutically acceptable emulsifyingagent to emulsify the desired amount of the compound or salt thereof.Particularly useful emulsifying agents include phosphatidyl cholines,and lecithin.

[0055] Further, the present invention provides liposomal formulations ofthe compounds disclosed herein and salts thereof. The technology forforming liposomal suspensions is well known in the art. When thecompound or salt thereof is an aqueous-soluble salt, using conventionalliposome technology, the same may be incorporated into lipid vesicles.In such an instance, due to the water solubility of the compound orsalt, the compound or salt will be substantially entrained within thehydrophilic center or core of the liposomes. The lipid layer employedmay be of any conventional composition and may either containcholesterol or may be cholesterol-free. When the compound or salt ofinterest is water-insoluble, again employing conventional liposomeformation technology, the salt may be substantially entrained within thehydrophobic lipid bilayer which forms the structure of the liposome. Ineither instance, the liposomes which are produced may be reduced insize, as through the use of standard sonication and homogenizationtechniques.

[0056] Of course, the liposomal formulations containing the compoundsdisclosed herein or salts thereof, may be lyophilized to produce alyophilizate which may be reconstituted with a pharmaceuticallyacceptable carrier, such as water, to regenerate a liposomal suspension.

[0057] Pharmaceutical formulations are also provided which are suitablefor administration as an aerosol, by inhalation. These formulationscomprise a solution or suspension of a desired compound described hereinor a salt thereof, or a plurality of solid particles of the compound orsalt. The desired formulation may be placed in a small chamber andnebulized. Nebulization may be accomplished by compressed air or byultrasonic energy to form a plurality of liquid droplets or solidparticles comprising the compounds or salts. The liquid droplets orsolid particles should have a particle size in the range of about 0.5 toabout 10 microns, more preferably from about 0.5 to about 5 microns. Thesolid particles can be obtained by processing the solid compound or asalt thereof, in any appropriate manner known in the art, such as bymicronization. Most preferably, the size of the solid particles ordroplets will be from about 1 to about 2 microns. In this respect,commercial nebulizers are available to achieve this purpose. Thecompounds may be administered via an aerosol suspension of respirableparticles in a manner set forth in U.S. Pat. No. 5,628,984, thedisclosure of which is incorporated herein by reference in its entirety.

[0058] Preferably, when the pharmaceutical formulation suitable foradministration as an aerosol is in the form of a liquid, the formulationwill comprise a water-soluble compound or a salt thereof, in a carrierwhich comprises water. A surfactant may be present which lowers thesurface tension of the formulation sufficiently to result in theformation of droplets within the desired size range when subjected tonebulization.

[0059] As indicated, the present invention provides both water-solubleand water-insoluble compounds and salts thereof. As used in the presentspecification, the term “water-soluble” is meant to define anycomposition which is soluble in water in an amount of about 50 mg/mL, orgreater. Also, as used in the present specification, the term“water-insoluble” is meant to define any composition which hassolubility in water of less than about 20 mg/mL. For certainapplications, water soluble compounds or salts may be desirable whereasfor other applications water-insoluble compounds or salts likewise maybe desirable.

[0060] The following Examples are provided to illustrate the presentinvention, and should not be construed as limiting thereof.

EXAMPLE 1 Synthesis of Compounds of Formula I

[0061] 2-[5(6)-Nitro-2-benzimidazoyl]-5-(4-nitrophenyl)furan wasprepared according to a modified literature procedure (R. Kada et al.,Collect. Czech. Chem. Comm. 38, 1700-1704 (1973)) by reaction of5-(4-nitrophenyl)furfural (10 mmol) with 4-nitro- 1,2-phenylenediamine(10 mmol) in a mixture of DMF (25 ml) and nitrobenzene (5 ml) at 150° C.for 22 h (under nitrogen). Cooling to room-temperature gave a suspendedsolid which was diluted with MeOH (30 ml), collected, and finally rinsedwell with ether. Yield: 2.56 g, 73%; mp 350-351° C. dec; lit mp 348-350°C.). ¹H NMR (DMSO-d₆): 7.51 (d, J=3.7 Hz, 1H), 7.57 (d, J=3.7 Hz, 1H),7.78 (d, J=8.9 Hz, 1H), 7.94 (s, 1H), 8.14 (dd, J=8.9, 2.2 Hz, 1H), 8.17(d, J=8.8 Hz, 2H), 8.36 (d, J=9.1 Hz, 2H), 8.47 (d, J=1.7 Hz, 1H)(benzimidazole NH not observed).

[0062] 2-[5(6)-Amino-2-benzimidazoyl]-5-(4-aminophenyl)furan. To asuspension of 2-[5(6)-nitro-2-benzimidazoyl]-5-(4-nitrophenyl)furan(2.63 g, 7.5 mmol) in EtOH (100 ml) was added stannous chloridedihydrate (16.0 g, 71 mmol) and the mixture was refluxed under nitrogenwith vigorous stirring for 3 hr to give a solution. After stirring atroom-temperature overnight, the solution was made basic by addition ofaqueous NaOH and the solids were extracted with EtOAc. After drying(Na₂SO₄) and filtering, the solvent was removed in vacuo and the residuewas dissolved in EtOH. This solution was then diluted with water to givea greenish yellow solid which was collected and dried in the desiccator(P₂O₅). Yield: 0.95 g, 44%; mp 161-165° C. dec. In contrast to thebis-nitro derivative, the ¹H NMR of this bis-amine was quite complexindicating it exists as a mixture of the two possible tautomers. The ¹HNMR of the hydrochloride salt, prepared by dissolving a sample of thefree base in HCl/EtOH followed by concentration, was less complex(DMSO-d₆, D₂O): 7.17 (d, J=8.6 Hz, 2H), 7.21 (d, J=3.7 Hz, 1H), 7.30(dd, J=8.7, 1.9 Hz, 1H), 7.63 (d, J=1.9 Hz, 1H), 7.74 (d, J=8.6 Hz, 1H),7.78 (d, J=3.8 Hz, 1H), 7.94 (d, J=8.6 Hz, 2H).

[0063] 2-[5(6)-Guanidino-2-benzimidazoyl]-5-(4-guanidinophenyl)furan. Toa chilled solution of2-[5(6)-amino-2-benzimidazoyl]-5-(4-aminophenyl)furan (0.363 g, 1.25mmol) and 1,3-bis(tert-butoxycarbonyl)-2-methyl-2-thiopseudourea (0.755g, 2.60 mmol) in dry DMF (25 ml) was added triethylamine (0.78 g, 7.71mmol) followed by mercury(II) chloride (0.78 g, 2.87 mmol) and theresulting suspension was stirred at ambient temperature for 3 days.After diluting with CH₂Cl₂ and filtering over Celite, the dark solutionwas washed well with saturated Na₂CO₃ solution, with water (3 times),and finally with brine. After drying (Na₂SO₄), the solvent was removedin vacuo and the remaining oil was diluted with MeOH to give theBOC-protected bis-guanidine as a pale green solid in two crops (0.58 g).The product was purified by reprecipitation from CH₂Cl₂/MeOH to give,after partial concentration a fluffy pale green solid (0.42 g, 43%),mp>400° C. dec, with darkening>300° C.

[0064] For deprotection, a solution of the protected bis-guanidine inCHCl₃ (12 ml) and EtOH (10 ml) was saturated with dry HCl at 0-5° C. andallowed to stir for 2 days at room-temperature to give a orange-coloredsuspension. After removing the solvents in vacuo, the solid was taken upin hot EtOH (60 ml), a small amount of insoluble material was filteredoff, and the solvent was again removed. After trituration with ether,the yellow solid was collected and dried in vacuo for 3 days at 50-60°C. Yield: 0.24 g, 92% (40% overall from the bis-amine). ¹H NMR(DMSO-d₆): 7.24 (d, J=8.6 Hz, 1H), 7.33 (d, J=3.6 Hz, 1H), 7.38 (d,J=8.6 Hz, 2H), 7.51 (br s, 3H), 7.57 (s, 1H), 7.64 (br s, 3H), 7.68(apparent s, 1H), 7.74 (d, J=8.6 Hz, 1H), 8.05 (d, J=8.5 Hz, 2H), 10.05(br s, 1H), 10.19 (br s, 1H). FABMS (thioglycerol): m/z 375 (100).FABHRMS:Calcd. for C₁₉H₁₈N₈O (MH⁺): 375.1682. Found: 375.1670. Anal.Calcd for C₁₉H₁₈N₈O.3HCl.2H₂O: C, 43.90; H, 4.85; N, 21.56; Cl, 20.46.Found: C, 43.68; H, 4.47; N, 20.68; Cl, 20.46.

[0065] 1-[ (5-Bromobenzo[b]furan-2-yl]-3-dimethylaminopropanehydrochloride. A mixture of 2-acetyl-5-bromobenzo[b]furan (23.9 g, 0.1mol), dimethylamine hydrochloride( 8.15 g, 0.1 mol), paraformaldehyde(3.6 g) and 2 ml of 35% hydrochloric acid in 150 ml of ethanol washeated at reflux for 20 h (TLC followed). The solvent volume was reducedunder reduced pressure to 50 ml and a mixture of acetone: ether (1:2)was added and the resultant solid was filtered, washed with ether anddried at 45° C. in a vacuum oven for 24 h to yield 23.0 g (69%), mp185-187° C. dec. ¹H NMR (DMSO-d₆): 8.07 (d, J=2.0 Hz, 1H), 7.91 (s, 1H),7.70 (d, J=8.8 Hz, 1H), 7.66 (dd, J=2.0 Hz, J=8.8 Hz, 1H), 3.58 (t,J=7.2, 2H), 3.41(t, J=7.2, 2H), 2.78(s,6H). ¹³C NMR (DMSO-d₆): 186.7,153.7, 152.2, 131.2, 128.8, 126.0, 116.2, 114.3, 113.5, 51.0, 42.2,33.3. The presence of small amount (ca. 5%) of the correspondingelimination product (vinyl ketone) was apparent from the ¹H NMR; theproduct was used directly in the next step with out furtherpurification.

[0066] 1-[(5-Bromobenzo[b]furan-2-yl]-4-(4-bromophenyl)butane-1,4-dione. A mixture of the aboveMannich base (16.6 g, 0.05 mol), 3-benzyl-5(2-hydroxyethyl)-4-methylthiazolium chloride catalyst( 0.68, 0.0025 mol), triethylamine (15.15 g,0.15 mol) and 4-bromobenzaldehyde (9.25 g, 0.05 mol) in 180 ml dioxanewas heated at reflux for 12 h (under nitrogen). The solvent was removedunder reduced pressure and the residue was treated with water. Theresultant gummy material was extracted with 150 ml of chloroform. Theorganic layer was dried over MgSO₄ and the solvent was removed underreduced pressure. The residue was treated with EtOH:ether(1:1) the solidwhich remained was filtered, washed with ether and dried to yield 7.4g(34%); mp 176-177° C.). ¹H NMR (DMSO-d₆): 8.03 (dd, J=0.4 and 1.5 Hz,1H), 7.91 (d, J=8.4 Hz, 2H), 7.82(d, J=0.4, 1H) 7.72 (d, J=8.4 Hz, 2H),7.68 (d, J=8.8, 1H) 7.64 (dd, J=1.5 and 8.8 Hz, 1H), 3.40-3.45 (m, 2H),3.37-3.33 (m, 2H). ¹³C NMR (DMSO-d₆): 197.3, 188.9, 153.5, 152.7, 135.2,131.5, 130.7, 129.6, 128.8, 127.0, 125.7, 115.9, 114.1, 112.4, 32.3,32.0. MS m/e 436 (M⁺). Anal. Calcd for C₁₈H₁₂Br₂O₃ C, 49.57; H, 2.77.Found: C, 49.49; H, 2.74.

[0067] 2-[(5-Bromobenzo[b]furan-2-yl]-5-(4-bromophenyl)furan. A solutionof the above diketone (8.72 g, 0.02 mol) in 150 ml CHCl₃:MeOH(1:1) wassaturated with HCl gas, stirred at room temperature for 4 h (TLCfollowed). The solvent was removed under reduced pressure and theresidue was stirred with 200 ml 10% aqueous NaHCO₃, filtered, washedwith water, dried and recrystallized from ether: CH₂Cl₂ (4:1) to yieldwhite solid 7.1 g(85%) mp 204-206° C. ¹H NMR (DMSO-d₆): 7.86 (d, J=2.0,1H)), 7.76 (d, J=8.4 Hz, 2H), 7.65(d, J=8.4, 2H) 7.58 (d, J=8.4 Hz, 1H),7.45 (dd, J=2.0 and 8.4 Hz, 1H) 7.23 (s, 1H), 7.17 (d, J=4.0 Hz, 1H),7.11(d, J=4.0 Hz, 1H). ¹³C NMR (DMSO-d₆): 152.9, 152.7, 148.0, 144.1,131.6, 130.4, 128.4, 127.0, 125.5, 123.3, 120.9 115.5, 112.7, 111.2,108.6, 101.1. MS m/e 436(M⁺). Anal. Calcd for C₁₈H₁₂Br₂O₃ C, 49.57; H,2.77. Found: C, 49.49; H, 2.74.

[0068] 2-[(5-Cyanobenzo[b]furan-2-yl]-5-(4-cyanophenyl)furan. A mixtureof the above dibromo compound (8.36 g, 0.02 mol) and CuCN( 5.34 g, 0.06mol) in 60 ml of N-methyl-2-pyrolidinone was heated at reflux for 4 h (under nitrogen), cooled, diluted with water and stirred with 200 ml of10% aqueous NaCN for 3 h. The solid was filtered, washed with water anddried. The crude product was dissolved in CHCl₃:MeOH(1:1) andchromatographed over neutral alumina to yield a pale yellow solid 4.35g(70%), mp 247-248° C. ¹H NMR (DMSO-d₆): 8.18 (d, J=1.6, 1H)), 7.98 (d,J=8.0 Hz, 2H), 7.88(d, J=8.0, 2H) 7.81 (d, J=8.4 Hz, 1H), 7.73 (dd,J=1.6 and 8.4 Hz, 1H) 7.41 (s, 1H), 7.38 (d,1H, J=3.6 Hz), 7.21(d,1H,J=3.6 Hz). ¹³C NMR(DMSO-d₆): 155.6, 152.4, 148.4, 144.7, 132.9, 132.6,128.8, 128.3, 126.1, 124.1, 118.6, 118.3, 112.3, 111.9, 111.2, 106.4,101.9. MS m/e 310(M⁺). Anal. Calcd for C₂₀H₁₀N₂O₂ C, 77.41; H, 3.25; N,9.02. Found: C, 77.41; H, 3.26; N, 8.95.

[0069] 2-[(5-Amidinobenzo[b]furan-2-yl]-5-(4-amidinophenyl)furandihydrochloride. The above dicyano compound (3.1 g, 0.01 mol) in 70 mlof ethanol was saturated with dry HCl gas at 0-5° C. and then stirred atroom temperature for 8 da (monitored by IR and TLC). Ether was added tothe mixture and the yellow imidate ester dihydrochloride was filteredand washed with ether. The solid was dried at 50° C. in a vacuum for 24h, to yield 4.3 g (93%). The solid was used directly in the next stepwithout further purification.

[0070] A suspension of imidate ester dihydrochloride (1.43 g, 0.003 mol)in 20 ml of ethanol was saturated with ammonia gas, stirred for 24 h andthe solvent was removed under reduced pressure. The solid was suspendedin water and the pH was adjusted to 9 and the off-white solid wasfiltered. The solid was stirred in HCl saturated ethanol and the yellowsalt was filtered and dried in a vacuum oven at 75° C. for 24 h to yield0.7 g (68%) mp 320 dec. ¹H NMR (DMSO-d₆/D₂O): 8.20 (d, J=1.2, 1H)), 8.01(d, J=8.0 Hz, 2H), 7.74(d, J=8.0, 2H) 7.82 (d, J=8.4 Hz, 1H), 7.78 (dd,J=1.2 and 8.4 Hz, 1H) 7.47 (s, 1H), 7.37 (d,1H, J=3.6 Hz), 7.20(d,1H,J=3.6 Hz). ¹³C NMR (DMSO-d₆): 165.7, 164.8, 156.7, 152.8, 148.6, 145.0,134.0, 128.9, 128.7, 126.4, 124.9, 123.9, 123.3, 122.0, 112.1, 111.8,111.2, 102.5. FABMS m/e 345(M⁺+1).Anal. Calcd forC₂₀H₁₆N₄O₂.2HCl.0.5H₂O: C, 56.36; H, 4.49; N, 13.14. Found: C, 56.73; H,4.71; N, 12.71.

EXAMPLE 2 DNA Fingerprinting Studies

[0071] In order to characterize the DNA recognition properties of aseries of analogs of furamidine (shown in FIG. 1), quantitative DNAaseIfootprinting studies were conducted using of a number of derivativeswith several different DNA sequences. Plasmid DNA restriction fragmentswere prepared and DNaseI footprinting experiments were conducted asdescribed in C. Bailly, et al., Biochemistry 35, 1150 (1996) and C.Bailly et al., Anti Cancer Drug Design (in press, 1999).

[0072]FIG. 2. illustrates the results of a quantitative DNase Ifootprinting titration experiment with the compound DB293 on a 265 bpDNA fragment as described herein. The EcoRI-PvuII restriction fragmentfrom plasmid pBS was 3′-end labeled at the EcoRI site with [α-³²P]dATPin the presence of AMV reverse transcriptase. As illustrated in FIG. 2A,the products of the DNase I digestion were resolved on an 8%polyacrylamide gel containing 8M urea. Drug concentrations are (lanes1-11) 0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.8, 2.1, 2.4, 2.7, 3.0 μM for DB 293and (lanes 12-15) 0, 1, 2 and 5 μM for DB270. Tracks labeled ‘G’represent dimethylsulphate-piperidine markers specific for guanines. Thetrack labeled DNA contained no drug and no enzyme. Numbers at the rightside of the gel refer to the numbering scheme of the fragment. Therectangles on the left side refer to the positions of (open box) anAT-rich and (filled box) a GC-rich binding site for DB293. FIG. 2B is agraphical illustration of footprinting plots for the binding of DB293 to(open circles) the AT site 5′-AATTAA and (filled squares) the GC-richsite 5′-ACCATG. The relative band intensity R corresponds to the ratioI_(C)/I_(o) where I_(c) is the intensity of the band at the ligandconcentration c and I_(o) is the intensity of the same band in theabsence of DB293. The differential cleavage plots shown in FIG. 2Ccompare the susceptibility of the DNA to cutting by DNase I in thepresence of (filled circles) 5 μM DB270 or (open squares) 1.5 μM DB293.Deviation of points towards the lettered sequence (negative values)corresponds to a ligand-protected site and deviation away (positivevalues) represents enhanced cleavage. The vertical scale is in units ofln(f_(a))−ln(f_(c)), where f_(a) is the fractional cleavage at any bondin the presence of the drug and f_(c) is the fractional cleavage of thesame bond in the control. The results are displayed on a logarithmicscale. The rectangles below the sequence show the positions of (openbox) the AT binding site and (filled box) the GC-rich site.

[0073] Results with the symmetric compounds furamidine and thebisbenzimidazole DB270 are as expected for AT specific minor-groovebinding agents and agree with observations on other furan derivativesand related compounds. With the asymmetrical compound DB293 (FIG. 1),however, the footprinting results present a number of surprises in theform of strong footprints in unexpected GC-rich regions, as shown inFIG. 2. In the 90-100 base region of the 265 mer pBS fragment in FIG. 2,for example, DB293 gave a very strong footprint while DB270 andfuramidine give negligible footprints. The most surprising feature ofthe footprint in this sequence region is its GC content relative to theAT rich sequences, where footprints are usually observed withminor-groove agents Quantitative analysis of the footprinting datareveals that the C₅₀ value, the drug concentration required forhalf-maximal footprinting, at the ATGA site is significantly lower thanat the neighboring ATTA site, indicating that DB293 prefers the siteincluding a GC base pair over the site containing only AT base pairs.The differential cleavage plots show that both DB270 and DB293 bindsimilarly to sites composed exclusively of AT base pairs (FIG. 2).Footprinting studies with several restriction fragments showed DB293,but not DB270, strongly binds to sites containing GC base pairs, such asATGA, ACGA, and ATGT.

EXAMPLE 3 Thermal Melting Experiments

[0074] In order to investigate the complexes of these compounds in moredetail with GC rich sequences, a hairpin duplex model containing the93-104 base sequence region from the 265 mer pBS restriction fragmentwas synthesized and is illustrated as oligo2 in FIG. 1. Oligo1 (alsoshown in FIG. 1) with the AATT sequence that has been used in theanalysis of a large number of minor-groove agents provides a reference.

[0075] Thermal melting experiments were conducted with a Cary 4spectrophotometer interfaced to a microcomputer. A thermistor fixed intoa reference cuvette was used to monitor the temperature. The oligomerswere added to 1 mL of buffer (0.01 M MES and 0.001M EDTA) in 1 cm pathlength reduced volume quartz cells, and the concentration was determinedby measuring the absorbance at 260 nm. Experiments were generallyconducted at a concentration of 2×10⁻⁶ M for hairpin oligo2, and 3×10⁻⁶M for hairpin oligo2- 1. Tm experiments for the complexes were conductedas a function of ratio.

[0076] Tm determinations of oligo2 on titration with DB293 gave up to a30° C. increase in Tm and did not level off until a ratio of 4:1DB293:hairpin duplex had been reached. The high ratio of DB293 tooligomer duplex was surprising for a duplex of only 13 base pairs. Inorder to better understand the nature of the complex, divided oligo2 wasdivided into two similar hairpin duplexes, oligo2-1 and oligo2-2 (FIG.1). As an illustration of the results obtained, derivative Tm curves ofDB270 and DB293 complexes with oligo2-1 are shown in FIG. 5. The DB293complex has a biphasic melting curve at a 1:1 ratio with a hightemperature phase and a low temperature phase near the Tm of the freehairpin duplex. At a 2:1 ratio, the low temperature phase disappears andonly the high temperature transition is present. Melting curves of DB270and furamidine complexes with oligo2-1 have single transitions at 1:1and 2:1 ratios with melting temperatures below the DB293 value. As withthe footprinting experiments, these results illustrate the dramaticdifferences in DNA interactions between the symmetric compounds relativeto the unsymmetric DB293. In addition, the Tm ratio results suggest thatthe unusual DNA recognition properties of DB293 are due to formation of2:1 complexes with oligo2-1 and 2-2, and a 4:1 complex with oligo2. Suchdimer complexes could also explain the unexpected footprinting behaviorof DB293, however, based on the +2 charge of DB293, dimer complexes arenot expected.

EXAMPLE 4 Surface Plasmon Resonance Experiments

[0077] To pursue the comparative quantitative analysis of thesecompounds with DNA in more detail by using surface plasmon resonance,5′-biotin labeled analogs of oligo2-1 and 2-2 were immobilized on aBIAcore four-channel streptavidine-coated sensor chip as follows:Immobilization of DNA and surface plasmon resonance (SPR) bindingstudies: 5′-biotin labeled hairpins were purchased with HPLCpurification (Midland Co). Samples of the DNA in MES10 buffer (0.01M MESand 0.001M EDTA, with 0.1M NaCl) at 50 nM concentration were applied toa BIAcore SA (streptavidin) chip by direct flow at 5 μl/min in a BIAcore2000 SPR instrument. Nearly the same amount of oligo1, oligo2-1 andoligo2-2 were immobilized on the surface of the SA chip. Steady stateanalysis was performed with multiple injections of differentconcentrations of each compound over the SA surface at a flow rate of 20μl/min, at 25° C.

[0078] Oligo1 was immobilized as a control sequence and one flow cellwas left as an unmodified reference. Binding results from the SPRexperiments were fit with either a single site model (K₂=0) or with atwo site model: r=(K₁*C_(free)+2* K₁*K₂*C_(free)²)/(1+K₁*C_(free)+2*K₁*K_(2*)C_(free) ²) where r represents the moles ofbound compound per mole of DNA hairpin duplex, K₁ and K₂ are macroscopicbinding constants, and C_(free) is the free compound concentration inequilibrium with the complex. The free compound is fixed by theconcentration in the flow solution. Binding of all of the furanderivatives to oligo1 is best fit by the single site model, whilebinding of DB293 to oligo2-1 and 2-2 requires the two site model and K₂is found to be much greater than K₁ as expected for interactions withvery large positive cooperativity. Oligos 1 and 2-1 are shown in FIG. 3to illustrate the differences.

[0079] The binding of all of the furan compounds to oligo1 is similarand saturation is reached at a 1:1 ratio, as expected from results witha number of minor-groove binding cations with DNA duplexes containing anAATT sequence. The results for DB293 binding to oligo2-1 and 2-2 are,however, dramatically different from results with the symmetriccompounds, and are dramatically different from the results obtained witholigo1 and DB293. Scatchard plots for binding of DB293 and DB270 are setforth in FIG. 3.

[0080] As in footprinting experiments with AT sites (FIG. 2), DB270 andDB293 bind in a very similar manner to oligo I with linear Scatchardplots indicating one type of strong binding site that binds a singlemolecule of DB270 or DB293 with binding constants of 2.3−2.6×10⁷.Binding of DB270 to oligo2-1 is at least a factor of ten weaker than itsbinding to oligo1 and probably represents its interaction at the TATsequence in the oligomer that is too short to form a very strongminor-groove complex. As shown in FIG. 3, however, binding of DB293 witholigo2-1 is highly cooperative and saturates at two molecules of DB293per oligo2-1 hairpin duplex. Fitting of the binding results to a twosite model to determine the macroscopic binding constants gave a bindingconstant (K₁) of 2.8×10⁶ for initial binding and a K₂ of 7.3×10⁷ forbinding to the second site after the first site is filled. Very similarresults are obtained for binding of DB293 to oligo2-2. The similarity ofbinding constants for DB270 and the first molecule of DB293 binding tooligo2-1 and 2-2 suggests that these are similar processes. The dramaticdifference occurs when the second molecule of DB293 binds cooperativelywith a K₂ that is over 25 times larger than for binding of DB270 and thefirst molecule of DB293 (K₁) to the oligomers. These results stronglysuggest that the unusual footprinting pattern observed with DB293 is dueto formation of a highly cooperative 2:1 complex in specific DNAsequences. The close analogs, furamidine and DB270, do not bind stronglyor footprint in these DNA sequences. Since all three furan compounds aredications, it is clearly structure, and not charge, that prevents thesymmetric derivatives from forming the dimer complex.

EXAMPLE 5 Structural Studies of Furan Derivatives

[0081] Structural studies of a number of furan derivatives witholigomers containing the AATT sequence of oligo1, including X-raystructures of furamidine and alkyl derivatives, have clearlydemonstrated a 1:1 classical minor-groove binding complex in which theamidine groups interact with the edges of A and T bases at the floor ofthe groove in the AATT site. See C. A. Laughton, Biochemistry 35, 5655(1996) and S. Neidle, Biopolymers 44, 105 (1997). This is the type ofcomplex expected from the experimental results of the furans of FIG. 1with oligo1. In order to characterize the 2:1 complex of DB293, NMRstudies of the DB293-oligo2-1 complex were initiated. All NMR spectrawere acquired with a Varian Unity Plus 600 MHz spectrometer. Typicalconditions for the collection of spectra in D₂O: 2 s relaxation delay,0.6 mL sample in a 5 mm NMR tube, and 1.0 Hz line broadening beforeFourier transformation. Two-dimensional experiments were obtained with aspectral width of 6000 Hz in both dimensions with 2048 complex datapoints in the t2 dimension and 512 points in the t1 dimension, while 1Dspectra were collected with a spectral width of 6000 Hz and 32K datapoints.

[0082] In proton NMR titrations of the oligomer duplex with DB293 onlytwo DNA species are detected at a 1:1 molar ratio. The two species areclearly illustrated with 2D COSY spectra in FIG. 4 for the aromatic tothymine methyl NMR spectral region. The free DNA has six well resolvedTH6-TCH₃ cross peaks as expected for the six T residues in the oligomer.In the 1:1 ratio complex there are 12 cross peaks as expected for twospecies in slow exchange, and one species has the same chemical shiftsas the free DNA. At the 2:1 ratio the free DNA signals disappear and thesignals for the 2:1 complex double in intensity. The 2:1 complex and thefree DNA are the only species observed in the 1:1 ratio COSY spectrum(FIG. 4) in agreement with the high cooperativity observed in thebinding experiments. No intermediate signals for a 1:1 complex can bedetected in any experiments throughout the titration of oligo2-1 withDB293, and the two species that we observe at the 1:1 ratio are freeoligomer and the 2:1 complex. In 2D NOESY analysis strong signals areobtained for the C H5-H6 interactions, and again only signals for freeDNA and the 2:1 complex are detected (not shown). In contrast, two setsof cross peaks are detected for DB293 in the oligo2-1 complex asexpected for two distinct bound molecules in slow exchange. Cross peaksbetween the two DB293 molecules and from DB293 to DNA minor-grooveprotons clearly show that the compound binds in the minor groove as anantiparallel dimer and makes contact with both DNA strands. Strongcrosspeaks from the two bound DB293 molecules to DNA base pairs fromT4.A15 to C7.G12 are observed and these interactions place the dimer inthe ATGA sequence that is common to both oligo2-1 and 2-2.

[0083] From these results it is clear that all three furan derivativesof FIG. 1 bind to the AATT sequence in oligo1 as classical minor-groovemonomer complexes. The symmetric compounds such as DB270 and furamidinedo not form the dimer species in a DNA complex and, therefore, do notbind to DNA sequences that do not have classical AT minor-groove bindingsites. DB293 forms an antiparallel, stacked dimer in complex with DNAsites that contain ATGA and probably other sequences. The dimer complexprovides a new motif for understanding and design of compounds that canrecognize DNA sequences containing both AT and GC base pairs. Theresults presented herein show that the binding of aromatic dications tomixed DNA sequences is exquisitely sensitive to compound structure andDNA sequence. Although Applicants do not wish to be bound by any theoryof the invention, it appears that the reasons for the cooperativeformation of the DB293 dimer complex are encoded in the interactionsbetween a specific DNA sequence and the orientation of chemical groupsin the dimer. Favorable stacking of DB293 to give a dimer in the contextof the anionic DNA minor groove can also contribute to the 2:1 complex.

[0084] The foregoing is illustrative of the present invention and is notto be construed as limiting thereof. The invention is defined by thefollowing claims, with equivalents of the claims to be included therein.

That which is claimed is:
 1. A compound of Formula I:

wherein: X is selected from the group consisting of O, S, and NH; Y isCH or N; A is CH or N; B is selected from the group consisting of NH, Oor S; R₁ is selected from the group consisting of H, loweralkyl,halogen, oxyalkyl, oxyaryl, and oxyarylakyl; R₂ and R₉ are eachindependently selected from the group consisting of H, H₂, hydroxy,lower alkyl, cycloalkyl, aryl, alkylaryl, alkoxyalkyl,hydroxycycloalkyl, alkoxycycloalkoxy, hydroxyalkyl, aminoalkyl andalkylaminoalkyl; and R₃, R₄, R₁₃ and R₁₄ are each independently selectedfrom the group consisting of H, lower alkyl, alkoxyalkyl, cycloalkyl,aryl, alkylaryl, hydroxyalkyl, aminoalkyl, and alkylaminoalkyl, or R₃and R₄ together or R₁₃ and R₁₄ together represent a C₂ to C₁₀ alkyl,hydroxyalkyl, or alkylene, or R₃ and R₄ together or R₁₃ and R₁₄ togetherare:

 wherein n is a number from 1 to 3, and R₁₀ is H or —CONHR₁₁NR₁₅R₁₆,wherein R₁₁ is lower alkyl and R₁₅ and R₁₆ are each independentlyselected from the group consisting of H and lower alkyl; L is selectedfrom the group consisting of:

 wherein R₅, R₆, R₇, and R₈ are each individually selected from thegroup consisting of H, alkyl, halo, aryl, arylalkyl, aminoalkyl,aminoaryl, oxoalkyl, oxoaryl, and oxoarylalkyl; and wherein saidcompound of Formula I binds the minor groove of DNA as a dimer.
 2. Thecompound of Formula I, wherein L is:

A is N, B is NH, X is O, Y is CH, R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₄are each H, and R₃ and R₁₃ are each H₂.
 3. The compound of Formula I,wherein L is:

A is N, B is NH, X is O, Y is CH, R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₄are each H, and R₃ and R₁₃ are each H₂.
 4. A method of binding mixedsequence DNA comprising contacting a sample DNA with a compound ofFormula (I):

wherein: X is selected from the group consisting of O, S, and NH; Y isCH or N; A is CH or N; B is selected from the group consisting of NH, Oor S; R₁ is selected from the group consisting of H, loweralkyl,halogen, oxyalkyl, oxyaryl, and oxyarylakyl; R₂ and R₉ are eachindependently selected from the group consisting of H, H₂, hydroxy,lower alkyl, cycloalkyl, aryl, alkylaryl, alkoxyalkyl,hydroxycycloalkyl, alkoxycycloalkoxy, hydroxyalkyl, aminoalkyl andalkylaminoalkyl; and R₃, R₄, R₁₃ and R₁₄ are each independently selectedfrom the group consisting of H, lower alkyl, alkoxyalkyl, cycloalkyl,aryl, alkylaryl, hydroxyalkyl, aminoalkyl, and alkylaminoalkyl, or R₃and R₄ together or R₁₃ and R₁₄ together represent a C₂ to C₁₀ alkyl,hydroxyalkyl, or alkylene, or R₃ and R₄ together or R₁₃ and R₁₄ togetherare:

 wherein n is a number from 1 to 3, and R₁₀ is H or —CONHR₁₁NR₁₅R₁₆,wherein R₁₁ is lower alkyl and R₁₅ and R₁₆ are each independentlyselected from the group consisting of H and lower alkyl; L is selectedfrom the group consisting of:

 wherein R₅, R₆, R₇, and R₈ are each individually selected from thegroup consisting of H, alkyl, halo, aryl, arylalkyl, aminoalkyl,aminoaryl, oxoalkyl, oxoaryl, and oxoarylalkyl; wherein said compound ofFormula I binds the minor groove of DNA as a dimer.
 5. The method ofclaim 4 wherein L is:

A is N, B is NH, X is O, Y is CH, R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₄are each H, and R₃ and R₁₃ are each H₂.
 6. The method of claim 4,wherein L is:

A is N, B is NH, X is O, Y is CH, R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₄are each H, and R₃ and R₁₃ are each H₂.
 7. A method of detecting mixedsequence DNA comprising contacting a sample of DNA with a fluorescentcompound of Formula (I):

wherein: X is selected from the group consisting of O, S, and NH; Y isCH or N; A is CH or N; B is selected from the group consisting of NH, Oor S; R₁ is selected from the group consisting of H, loweralkyl,halogen, oxyalkyl, oxyaryl, and oxyarylakyl; R₂ and R₉ are eachindependently selected from the group consisting of H, H₂, hydroxy,lower alkyl, cycloalkyl, aryl, alkylaryl, alkoxyalkyl,hydroxycycloalkyl, alkoxycycloalkoxy, hydroxyalkyl, aminoalkyl andalkylaminoalkyl; and R₃, R₄, R₁₃ and R₁₄ are each independently selectedfrom the group consisting of H, lower alkyl, alkoxyalkyl, cycloalkyl,aryl, alkylaryl, hydroxyalkyl, aminoalkyl, and alkylaminoalkyl, or R₃and R₄ together or R₁₃ and R₁₄ together represent a C₂ to C₁₀ alkyl,hydroxyalkyl, or alkylene, or R₃ and R₄ together or R₁₃ and R₁₄ togetherare:

 wherein n is a number from 1 to 3, and R₁₀ is H or —CONHR₁₁NR₁₅R₁₆,wherein R₁₁ is lower alkyl and R₁₅ and R₁₆ are each independentlyselected from the group consisting of H and lower alkyl; L is selectedfrom the group consisting of:

 wherein R₅, R₆, R₇, and R₈ are each individually selected from thegroup consisting of H, alkyl, halo, aryl, arylalkyl, aminoalkyl,aminoaryl, oxoalkyl, oxoaryl, and oxoarylalkyl; and wherein saidcompound of Formula I binds the minor groove of DNA as a dimer; and thenobserving fluorescence in the sample, the observation of fluorescenceindicating the compound of Formula I has bound to a sequence of DNA. 8.The method of claim 7, wherein L is:

A is N, B is NH, X is O, Y is CH, R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₄are each H, and R₃ and R₁₃ are each H₂.
 9. The method of claim 7,wherein L is:

A is N, B is NH, X is O, Y is CH, R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₄are each H, and R₃ and R₁₃ are each H₂.
 10. A pharmaceutical formulationcomprising a compound of Formula I:

wherein: X is selected from the group consisting of O, S, and NH; Y isCH or N; A is CH or N; B is selected from the group consisting of NH, Oor S; R₁ is selected from the group consisting of H, loweralkyl,halogen, oxyalkyl, oxyaryl, and oxyarylakyl; R₂ and R₉ are eachindependently selected from the group consisting of H, H₂, hydroxy,lower alkyl, cycloalkyl, aryl, alkylaryl, alkoxyalkyl,hydroxycycloalkyl, alkoxycycloalkoxy, hydroxyalkyl, aminoalkyl andalkylaminoalkyl; and R₃, R₄, R₁₃ and R₁₄ are each independently selectedfrom the group consisting of H, lower alkyl, alkoxyalkyl, cycloalkyl,aryl, alkylaryl, hydroxyalkyl, aminoalkyl, and alkylaminoalkyl, or R₃and R₄ together or R₁₃ and R₁₄ together represent a C₂ to C₁₀ alkyl,hydroxyalkyl, or alkylene, or R₃ and R₄ together or R₁₃ and R₁₄ togetherare:

 wherein n is a number from 1 to 3, and R₁₀ is H or —CONHR₁₁NR₁₅R₁₆,wherein R₁₁ is lower alkyl and R₁₅ and R₁₆ are each independentlyselected from the group consisting of H and lower alkyl; L is selectedfrom the group consisting of:

 wherein R₅, R₆,l R₇, and R₈ are each individually selected from thegroup consisting of H, alkyl, halo, aryl, arylalkyl, aminoalkyl,aminoaryl, oxoalkyl, oxoaryl, and oxoarylalkyl; in a pharmaceuticallyacceptable carrier.
 11. The pharmaceutical formulation of claim 10,wherein L is:

A is N, B is NH, X is O, Y is CH, R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₄are each H, and R₃ and R₁₃ are each H₂.
 12. The pharmaceuticalformulation of claim 10, wherein L is:

A is N, B is NH, X is O, Y is CH, R₁, R₂, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₄are each H, and R₃ and R₁₃ are each H₂.